1. School of Biology, Newcastle University, Ridley Building 2, Newcastle upon Tyne, NE1 7RU, UK
2. Laboratoire Microorganismes et Biomolécules Actives, Université Tunis El Manar (FST) and Université de Carthage (INSAT), 2092 Tunis, Tunisia
3. Central Facility for Microscopy, HZI – Helmholtz Centre for Infection Research, Inhoffenstraße7, 38124 Braunschweig, Germany